1. Field of the Invention
This invention relates to a tape transport system control device for an apparatus such as a VTR (video tape recorder) having a tape transport system which is arranged to cause a magnetic tape to travel, and more particularly to a tape transport system control device arranged to control the speed and tension of the tape over a wide range of speeds in a so-called reel-to-reel state by controlling both supply-side and takeup-side reel motors without using a capstan for controlling the tape speed.
2. Description of the Related Art
In a case where a tape transport system allows the tape to travel either at a predetermined speed or within a narrow range of speeds, the tape speed can be controlled by arranging between two reels a capstan which accurately rotates at a set speed. During recent years, however, there have arisen a desire for causing the tape speed to continuously vary over a wide range and a desire for controlling the tape tension accurately at a low tension value as the tape has become thinner. To satisfy these desires, it has become necessary to adopt a method called reel-to-reel control for controlling the tape speed and the tape tension by directly controlling each of reel motors.
In controlling the reel motor, it is necessary to cope with changes taking place in radius of rotation and in inertial mass as the amount of winding of the tape around the reel varies. Various methods have been contrived for coping with the changes of the characteristic of the reel including the tape. These methods are based mainly on the characteristic of each individual reel system. However, in a tape transport system, a tape payed out from a supply-side reel reaches a takeup-side reel through a complex path, including such a load system as an impedance roller which is a rotary post arranged to be of a large inertial mass for the purpose of suppressing the unnecessary vibrations of the tape. Therefore, in performing the reel-to-reel control, even if the characteristic of one reel system is arranged to be equal to that of the other, acceleration or deceleration of the travel of the tape brings about an unbalance in tape tension between the supply reel side and the takeup reel side because of the adverse effect of the load system. As a result, either a high tension is applied to the tape or the tape tension decreases too much.